8212988: add recent class unloading events to the hs_err log

Also moved class unloading logging in expected place.

Reviewed-by: never, stuefe

src/hotspot/share/oops/instanceKlass.cpp

@@ -75,6 +75,7 @@
 #include "services/classLoadingService.hpp"
 #include "services/threadService.hpp"
 #include "utilities/dtrace.hpp"
+#include "utilities/events.hpp"
 #include "utilities/macros.hpp"
 #include "utilities/stringUtils.hpp"
 #ifdef COMPILER1
@@ -2447,6 +2448,13 @@ void InstanceKlass::unload_class(InstanceKlass* ik) {
   // notify ClassLoadingService of class unload
   ClassLoadingService::notify_class_unloaded(ik);
 
+  if (log_is_enabled(Info, class, unload)) {
+    ResourceMark rm;
+    log_info(class, unload)("unloading class %s " INTPTR_FORMAT, ik->external_name(), p2i(ik));
+  }
+
+  Events::log_class_unloading(Thread::current(), ik);
+
 #if INCLUDE_JFR
   assert(ik != NULL, "invariant");
   EventClassUnload event;

src/hotspot/share/services/classLoadingService.cpp

@@ -137,11 +137,6 @@ void ClassLoadingService::notify_class_unloaded(InstanceKlass* k) {
       _class_methods_size->inc(-methods->at(i)->size());
     }
   }
-
-  if (log_is_enabled(Info, class, unload)) {
-    ResourceMark rm;
-    log_info(class, unload)("unloading class %s " INTPTR_FORMAT , k->external_name(), p2i(k));
-  }
 }
 
 void ClassLoadingService::notify_class_loaded(InstanceKlass* k, bool shared_class) {

src/hotspot/share/utilities/events.cpp

@@ -24,6 +24,7 @@
 
 #include "precompiled.hpp"
 #include "memory/allocation.inline.hpp"
+#include "oops/instanceKlass.hpp"
 #include "runtime/mutexLocker.hpp"
 #include "runtime/os.inline.hpp"
 #include "runtime/osThread.hpp"
@@ -37,6 +38,7 @@ EventLog* Events::_logs = NULL;
 StringEventLog* Events::_messages = NULL;
 StringEventLog* Events::_exceptions = NULL;
 StringEventLog* Events::_redefinitions = NULL;
+UnloadingEventLog* Events::_class_unloading = NULL;
 StringEventLog* Events::_deopt_messages = NULL;
 
 EventLog::EventLog() {
@@ -67,6 +69,7 @@ void Events::init() {
     _messages = new StringEventLog("Events");
     _exceptions = new StringEventLog("Internal exceptions");
     _redefinitions = new StringEventLog("Classes redefined");
+    _class_unloading = new UnloadingEventLog("Classes unloaded");
     _deopt_messages = new StringEventLog("Deoptimization events");
   }
 }
@@ -96,3 +99,16 @@ EventMark::~EventMark() {
     Events::log(NULL, "%s", _buffer.buffer());
   }
 }
+
+void UnloadingEventLog::log(Thread* thread, InstanceKlass* ik) {
+  if (!should_log()) return;
+
+  double timestamp = fetch_timestamp();
+  // Unloading events are single threaded.
+  int index = compute_log_index();
+  _records[index].thread = thread;
+  _records[index].timestamp = timestamp;
+  stringStream st = _records[index].data.stream();
+  st.print("Unloading class " INTPTR_FORMAT " ", p2i(ik));
+  ik->name()->print_value_on(&st);
+}

src/hotspot/share/utilities/events.hpp

@@ -165,9 +165,17 @@ class StringEventLog : public EventLogBase<StringLogMessage> {
     logv(thread, format, ap);
     va_end(ap);
   }
-
 };
 
+class InstanceKlass;
+
+// Event log for class unloading events to materialize the class name in place in the log stream.
+class UnloadingEventLog : public EventLogBase<StringLogMessage> {
+ public:
+  UnloadingEventLog(const char* name, int count = LogEventsBufferEntries) : EventLogBase<StringLogMessage>(name, count) {}
+
+  void log(Thread* thread, InstanceKlass* ik);
+};
 
 
 class Events : AllStatic {
@@ -189,6 +197,8 @@ class Events : AllStatic {
   // Redefinition related messages
   static StringEventLog* _redefinitions;
 
+  // Class unloading events
+  static UnloadingEventLog* _class_unloading;
  public:
   static void print_all(outputStream* out);
 
@@ -203,6 +213,8 @@ class Events : AllStatic {
 
   static void log_redefinition(Thread* thread, const char* format, ...) ATTRIBUTE_PRINTF(2, 3);
 
+  static void log_class_unloading(Thread* thread, InstanceKlass* ik);
+
   static void log_deopt_message(Thread* thread, const char* format, ...) ATTRIBUTE_PRINTF(2, 3);
 
   // Register default loggers
@@ -236,6 +248,12 @@ inline void Events::log_redefinition(Thread* thread, const char* format, ...) {
   }
 }
 
+inline void Events::log_class_unloading(Thread* thread, InstanceKlass* ik) {
+  if (LogEvents) {
+    _class_unloading->log(thread, ik);
+  }
+}
+
 inline void Events::log_deopt_message(Thread* thread, const char* format, ...) {
   if (LogEvents) {
     va_list ap;